When machining a work piece, the piece must be securely mounted in a vise on the machine so that the forces of machining do not move the piece and destroy precision. The mounting of the piece in the vise may consume a considerable portion of the labor cost of machining. U.S. Pat. No. 5,893,551 issued Apr. 13, 1999 to Cousins et al.; U.S. Pat. No. 5,649,694 issued Jul. 22, 1997 to Buck; and U.S. Pat. No 5,098,073 issued Mar. 24, 1992 to Lenz teach machine vises for simultaneously holding two pieces with a single stationary common jaw and two movable jaws that move toward the stationary jaw from opposite directions. Their inventions are limited to holding only two pieces at a time.